Electrical plug



Dec. 3, 1968 R. BlszKo 3,4l4,870

ELECTRI CAL PLUG Filed Aug. 2, 1966 United States Patent O "ice claims.(ci. 339-195) This invention, which is a continuation-in-part of Ser.No. 494,135, filed Oct. 8, 1965, now abandoned, relates to an improvedelectrical plug connection of the type commonly used with appliancessuch as toasters, irons, vacuum cleaners, etc., and more particularly toan electrical plug that can be locked into a receptacle to avoidaccidental disconnection.

Ordinarily, electrical plugs are designed with conductive prongs whichare arranged to frictionally engage resilient contacts in a receptacle.Such plugs are held in place solely by the frictional engagement betweenthe prongs and the receptacle contacts. However, this frictionalengagement is usually not sufficiently effective to prevent the plugfrom becoming accidently disconnected when a pull is exerted on theinsulated wire leading from the plug to the appliance being used.

A number of attempts have been made to resolve this problem, but to datenone have proved satisfactory. For example, some prior art plugs havebeen provided with notches on the prongs, the notches being designed tomechanically engage the receptacle walls. However, in order to placesuch notches in operative engagement with the receptacle, it hasheretofore been necessary to provide the plug with a resilient bodywhich can be squeezed together to facilitate insertion of the prongsinto the receptacle. Thereafter, the plug Walls are allowed to springbacl thus allowing the prongs to locate themselves in locked engagementwith the receptacle wall. Plugs of this type are relatively expensive tomanufacturc and in many cases, are not readily adaptable for use withconventional receptacles, Moreover, in order to disconnect plugs of thistype, it is necessary to first squeeze the resilient plug walls togetherto disengage the prongs from their locked positions. This particularfeature can prove dangerous, particularly when an operative emergency isencountered requiring quick disconnection.

It is therefore an object of the present invention to provide animproved electrical plug construction wherein means associated with theconductive prongs are provided for quickly and efficiently placing theplug in locked engagement with a conventional receptacle.

Another object of the present invention is to provide an electrical plugwhich may easily be removed from the receptacle in the case of anemergency.

A further object of the present invention is to provide a plugconstruction which is simple and inexpensive to manufacture and whichcan be employed with any conventional receptacle.

These and other objects of the present invention will become moreapparent as the description proceeds with the aid of the accompanyingdrawings in which:

FIG. 1 is a perspective view of an electric plug embodying the conceptsof the present invention;

FIG. 2 is a side elevational view of the plug shown in FIG. 1; and

FIG. 3 is a view partially in section showing the plug inserted andlocked in a conventional receptacle.

Referring initially to FIGS. 1 and 2 wherein are best shown generalfeatures of the invention, an electrical plug 6 is shown comprisedbasically of a plug body 10 having two substantially parallelelectrically conductive prongs 11 and 12 extending outwardly therefrom.The prongs, which may lbe attached 'by any known manner 3,414,870Patented Dec. 3, 1968 to the plug body, are each connected at one end asat 7 to the leads 8 of an insulated cord 9. The foregoing is descriptiveof conventional plug constructions and is not considered as part of thepresent invention.

One edge of each of the prongs 11 and 12 is provided with a lockingnotch 13 which extends from the face 21 of the plug body 10 to ashoulcler 16. The opposite edge of each prong may 'be similarly providedwith a second looking notch 14 which terminates in a shoulder 15.

The purpose served by the locking notches 14 and 15 will now bedescribed in detail by further reference to FIG. 3 which includes asectional view of a conventional receptacle assembly R. The receptacleincludes a wall 19 enclosing resilient contacts 18 (only one of which isshown), the latter being connected in a conventional manner to a powersource. As shown in FIG. 3, the plug 6 is in locked operative engagementwith receptacle R. This engagement is achieved by the followingprocedure: first, the prongs 11 and 12 of plug 6 are inserted axiallyinto spaced slots 17 located in the front face of receptacle wall 19.The direction of initial insertion is indicated diagrammatically by thearrow A, it being understood that the width of the unnotched prongportions is slightly less than the width of slots 17. When fullyinserted, the prongs are in frictional engagement with the contacts 18.Once fully inserted, plug 6 is then pressed downwardly in a transversedirection indicated diagrammatically by the arrow B. This transversemovement causes the bottom edge of each wall slot 17 to enter into thelooking notches 13 and thus become mechanically engaged against theShoulders 16. Such mechanical engagement effectively prevents the plugfrom accidentally being withdrawn from the receptacle in a directionopposite to that of arrow A without first being transversely raised todisengage the notches 13 from the front face of the receptacle Wall.

In some instances, the distance between the contacts 18 and the frontface of receptacle wall 19 may be much less than that shown in FIG. 3.Under these circumstances, the plug 6 may simply be rotated prior toinsertion n order to permit placement of the lower notches 14 in lockedengagement, thus avoiding the danger of damaging the receptacle contacts18 by overinsertion of the prongs 11 and 12. The manner of locking theplug into place when using notches 14 is, however, identical to thatpreviously described in connection with notches 13.

The above-described construction provides several significant advantagesover prior art plug constructions. To begin with, the locked engagementafforded by the notched prongs 11 and 12 eifectively prevents accidentaldisconnection of the plug from the receptacle during normal operation.This looking engagement is made possible without resorting to expensivespecially constructed plug bodies, and thus avoids undue expenditures.An important advantage also lies in the fact that by grasping the cord 9and simply moving it rapidly up and down, the prongs 11 and 12 will bedisplaced in a transverse direction, thus causing the locking notches 13(or 14 if such be the case) to become disengaged. Once this has beenaccomplished, the plug may simply be withdrawn from the receptacle bypulling on cord 9. This feature avoids the necessity of grasping theplug itself and in some instances when an operative emergency isencountered, may be of considerable i-mportance.

Finally, it is important to note that a plug constructed in accordancewith the foregoing description may be employed with all types ofconventional receptacles, as opposed to some prior art constructionswhich require both the plug and receptacle to be specially constructed.

It is my intention to cover all changes and modifications of theembodiment herein described which do not depart from the spirit andscope of the invention.

I claim:

1. An electrical plug construction comprising in combinaton: a plugbody; at least two electrically conductive prongs extending outwardly ina substantially parallel relationship from said plug body, said prongsbeing adapted for axial insertion through suitably spaced slots in thewall of a conventional electrical receptacle, and locking means on saidprongs for cooperating With said wall to prevent removal in a reverseaxial direction of said prongs from said receptacle, said locking meansbeing operatively engaged with said wall by transverse displacement ofsaid plug relative to said receptacle.

2. The apparatus as set forth in claim 1 Wherein said locking means iscomprised of a locking notch on one edge of each said prongs, saidnotches terminating in shoulders adapted to engage the Wall of saidreceptacle upon transverse displacement of said plug.

3. The apparatus as set forth in claim 2 further characterized by anadditional notch on the opposite edge of each said prongs.

4. The apparatus as set forth in claim 3 wherein the notches on eachsaid prongs are of different lengths.

5. The apparatus as set forth in claim 4 further characterized by saidplug body being fabricated of a dielectric rigid substance.

References Cited UNITED STATES PATENTS 2,170,359 8/1939 Wirth 339 133 X2,487,509 11/1949 Baker 339-91 X 2,923,909 2/1960 Modrey 339 176 XMARVIN A. CHAMPION, Primd/'y Examiner. JOHN R. MOSES, Assistant Examner.

1. AN ELECTRICAL PLUG CONSTRUCTION COMPRISING IN COMBINATION: A PLUG BODY; AT LEAST TWO ELECTRICALLY CONDUCTIVE PRONGS EXTENDING OUTWARDLY IN A SUBSTANTIALLY PARALLEL RELATIONSHIP FROM SAID PLUG BODY, SAID PRONGS BEING ADAPTED FOR AXIAL INSERTION THROUGH SUITABLY SPACED SLOTS IN THE WALL OF A CONVENTIONAL ELECTRICAL RECEPTACLE, AND LOCKING MEANS ON SAID PRONGS FOR COOPERATING WITH SAID WALL TO PREVENT REMOVAL IN A REVERSE AXIAL DIRECTION OF SAID PRONGS FROM SAID RECEPTACLE, SAID LOCKING MEANS BEING OPERATIVELY ENGAGED WITH SAID WALL BY TRANSVERSE DISPLACEMENT OF SAID PLUG RELATIVE TO SAID RECEPTACLE. 